Relay permutation-type switching system



Jan. 13, 1953 A. E. JOEL, JR

RELAY PERMUTATION-TYPE swncnmc SYSTEM 11 Sheets-Sheet 1 Filed Dec. 5,1947 lNl/E/VTOR AE. JOEL, JR. BY

W & Gnu.

ATTORNEY.

qmk Mum DEW Jan. 13, 1953 A. E. JOEL, JR

I RELAY PERMUTATION-TYPE SWITCHING SYSTEM 11 Sheets-Sheet 2 Filed Dec.5, 1947 R w M ma w W m NJ. 0 /E Jan. 13, 1953 A. E. JOEL, JR

RELAY PERMUTATION-TYPE SWITCHING SYSTEM NmkmEmw NMQQQ kXmEE 70 t O Qm RMmm 0 I s NE t 0 J 0 m\ WE l o W 1 A mu Y B m W\\ m 9 l 5 c m wt 8 D d en F NNE NMLMGMNQMQEE ATTORNEY Jan. 13, 1953 A. E. JOEL, JR

- RELAY PERMUTATION-TYPE SWITCHING SYSTEM 11 Sheets-Sheet 4 Filed D80.5, 1947 //V VE/V T0)? 45. JOEL, JR.

ATTORNEY Jan. 13, 1953 A. E. JOEL, JR 2,625,610

' RELAY PERMUTATION-TYPE SWITCHING SYSTEM Filed D60. 5, 1947 llSheets-Sheet 5 ATTORNEY Jan. 13,1953 A. E. JOEL, JR 2,625,610 RELAYPERMUTATION-TYPE SWITCHING SYSTEM Filed Dec. 5, 1947 ll Sheets-Sheet 6rewkxsLnm/a beau/r PEEMUTAWOA/ CONTZOL u/v/z CLZ INVENTOR AE. JOEL, JR.

ATT Off/1E Y TO OTHER Jan. 13, 1953 A. E. JOEL, JR 2,625,610

RELAY PERMUTATION-TYPE SWITCHING SYSTEM Filed Dec. 5, 1941' llSheets-Sheet 7 k B 2 k 2 2. g 5 k E g. Q

/N VENT 0R 4.5 JOELJR.

Jan. 13, 1953 A. E. JOEL, JR 2,625,610

RELAY RERMUTATION-TYPE SWITCHING SYSTEM Filed Dec. 5, 1947 llSheets-Sheet 8 INVENTOR 4.5 .1051. JR.

ATTORNEY Jan. 13, 1953 A. E. JOEL, JR

RELAY PERMUTATION-TYPE SWITCHING SYSTEM 11 Sheets-Sheet 9 Filed Dec. 5,1947 ATTORNEY Jan. 13, 1953 A. E. JOEL, JR

RELAY PERMUTATION-TYPE SWITCHING SYSTEM 11 Sheets-Sheet 10 Filed Dec. 5,1947 lNl EN TOR A. E. JOEL, JR. By

A T TORNE Y Jan. 13, 1953 A. E. JOEL, JR ,6

RELAY PERMUTATION-TYPE SWITCHING SYSTEM Filed Dec. 5, 194? llSheets-Sheet 11 lA/VENTOR AE. JOEL,JR. BY

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V w w T A Patented Jan. 13, 1953 RELAY PERMUTATION-TYPE SWITCHING SYSTEMAmos E. Joel, J r., New York, N. Y., assignor to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a. corporation of New YorkApplication December 5, 1947, Serial No. 789,789

14 Claims. 1

This invention relates to switching systems and particularly toelectro-magnetic switching such as automatic switching in telephone andtelegraph systems.

Objects of the invention are the provision of improved and simplifiedautomatic switching arrangements for interconnecting lines and trunks incommunication systems and an increase in the availability and efiiciencyin the use of groups of lines or trunks to establish desiredconnections.

This invention is a switching system in which any one of a plurality oflines or trunks in one group may be connected with any desired one of aplurality of lines or trunks in another group, th connecting means beingso arranged that the incoming lines or trunks may be connected to theoutgoing lines in any of the possible permutations of such connections.7

According to a feature of the invention a link circuit for connectingeach of a group of communication lines to any desired one of anothergroup of communication lines comprises successive stages of switchingrelays, each stage being arranged to connect one less line in eachgroup, whereby the lines of the first group may be connected to thelines of the other group by the operation of any one of the difierentcombinations of said switching relays.

According to another feature of the invention a pair of link circuits isprovided, each arranged for simultaneously connecting each line of afirst group to a difierent one of a second group of lines, whereby thelines of the first and second groups may be interconnected in any one ofthe possible different combinations, means being proe vided to changethe combination whenever it is desired that a particular line in thefirst group be connected to a different line in the second group,control means being provided to establish the new combination throughone of the links while the previous combination is maintained throughthe other link and then to establish the new combination through thesaid one of the links.

The invention and its features will be further explained by describing asystem in which the invention is embodied, one such system being shownschematically in the drawing which forms a part of this specification.The invention is not limited in its application to the particular typeof system shown, or to switching means of the type described, but isgenerally applicable to automatic switching and particularly incommunication systems.

Referring to the drawing, which consists of twelve figures and shows inschematic form an automatic telephone system:

Fig. 1 shows two subscriber stations and lines and two of a group ofline or incoming trunk circuits; 7

Figs. 2 and 3 show finder-register circuits FBI and FR2;

Fig. 4 shows a gate circuit;

Figs. 5 and 6 show two permutation control links CM and CLZ, apermutation link transfer relay and part of the permutation translatincircuit;

Figs. 7a and 71) show a permutation translating circuit;

Figs. 8 and 9 show permutation link circuits PL! and PL2; I

Fig. 10 shows two outgoing trunk circuits and two subscriber stations;

Fig. 11 shows an ntermediate trunk circuit; and

Fig. 12 shows the position in which Figs. 1 to 10 inclusive, are to beplaced to form an operative system.

General description The subscriber stations W, X, Y and Z shown in Figs.1 and 10 may be or the usual common battery type provided in automatictelephone systems, each including a dial Ior transmitting digit impulsesto control the establishment of desired connections. Each or thestations W and X are shown connected directly by lines LI and L6 to theincoming trunk circuits Tl and T6 whereby these trunk circuits take onthe character of line circuits. The iines LI and Lt may, however, beconnected through line finders or other intermediate switching devicesto the trunk circuits. While not shown, a permutation link may be used.as a finder switching stage. Each of the trunk circuits TI and T6 isarranged to provide talking battery through the windings of relay A tothe associated calling station and through the windings of relay D to aconnected called line; and voice currents are transmitted throughcondensers TCl and T02. Relay B is a slow to release relay whichconnects busy marking and holding ground potential to the sleeveconductor l4. Re-

lay CT, when operated, connects the associated calling line to afinder-register circuit FRI or FR2. Relay RG controls the transmissionof a ringing signal to the connected called line; and relay BB operatesin case the called line is busy to transmit a busy tone to the callingstation.

The intermediate trunk circuit shown in Fig. 11 is similar to theincoming trunk circuits l and 2 except that it is not arranged forfeeding talking battery to subscriber stations. 7

Each of the two finder-registers FRI and PR2 shown in Figs. 2 and 3comprises a rotary finder switch Fl or F2, a rotary register switch RIor R2 and a plurality of control relays. The finder switch has astepping magnet and 8 wipers and associated terminal banks through whichthe finder has access to each of the incoming trunks in a groupincluding the trunk circuits l and 6 shown in Fig. 1. The finderswitches are of the stay-put type and are self-allotting; so that one ofthem is started in operation when an incoming trunk circuit is seized,as hereinafter described in detail. The register switch of eachfinder-register circuit comprises a stepping magnet, a release magnet,four wipers and associated terminal banks. The wipers have a normalposition to which they are restored at the end of a cycle of operation.

The gate circuit shown in Fig. 4 comprises line relays IIII and I02, onefor each finder-register circuit and a common gate relay I and auxiliarycontrol relays I06, I08, III, H2 and H3, arranged to operatively connectthe finder-registers, one or more at a time, with the permutationcontrol and translating circuits. 7 y

The permutation link circuits PLI and PL2 are each arranged tointerconnect a group of six subscriber lines or incoming trunks with agroup of six outgoing or intermediate trunks or subscriber lines. Eachpermutation link comprises an incoming line cut-through relay I95 orIQ'I, an outgoing line cut-through relay I96 or I98, and elevenswitching relays FBI to PRII for connecting the six incoming lines withthe six outgoing lines in each of the different connecting arrangementswhich are possible. Each of switching relays PRI, PR2 and PR3 hascontacts for connecting six incoming lines with six outgoing lines; eachof switching relays PR4, PR5 and PR5 has contacts for connecting fiveincoming lines with live outgoing lines; each of switching relays PR!and PR8 has contacts for connecting four incoming lines with fouroutgoing lines; each of switching relays PR9 and FBI 0 has contacts forconnecting three incoming lines with three outgoing lines; and switchingrelay PRII has contacts for connecting two incoming lines with twooutgoing lines. While the links shown are arranged to connect an equalnumber of incoming and outgoing lines, this is not necessary and eachgroup may include any number of lines. The relays ULI and ULZ shown inFigure 8 together with relay TF shown in Fig. 6 constitute a transfercircuit controlling the alternate use of the permutation links and theirconnection to the permutation control link and translating circuits. V iv The permutation control link CLZ shown in Fig. 6 comprises relays FBIto PRII which are connected, under control of the transfer relay TF, foroperation to register the same connecting combination as exists in theconnected one of the permutation links PLI and PL2. The permutationcontrol link CLI shown in Fig. 5 comprises relays PRI to PRII which areoperatively controlled by the permutation translating circuit of Figs.7a and 7b to register the new combination to which the one or the otherof the permutation links is to be operated to establish the new desiredconnections, as registered by the finder-register circuits which are atthat time operatively connected to the permutation control link andtranslating circuits, and to also register the old connections which areto be continued.

The permutation translating circuit comprises the outgoing trunk relaysOI to 06 shown in Fig. 6 and a plurality of relays in Figs. 7a and 7bfor effecting the operation of the permutation control link CLI asrequired to control the switching relays of the one or the other of thepermutation links to establish a new connecting combination which willcontinue the existing connections between calling and called trunks orlines and which will also establish connection of other calling andcalled trunks or lines as registered by the finder-register circuitsthen in operative connection with the permutation control andtranslating circuits.

When a call is initiated at a subscriber station and the calling line isconnected to one of the incoming trunk circuits TI to T6, the finderswitch of an idle one of the finderregisters FRI and FRZ is operated toconnect the associated register switch through the incoming trunkcircuit to the calling line. When the calling subscriber dials the digitrepresenting a called line, the register switch is selectivelypositioned to mark the corresponding outgoing trunk. As soon thereafteras the permutation control links and translating circuit are idle, thegate circuit operates to connect the'finder-register in question to thetranslating circuit. All finder-registers which have been selectivelyoperated to register the called line digit, are simultaneously connectedwith the translating circuit by the operation of the gate relay Hit] ofthe gate circuit, whereby'one or more of the outgoing trunk relays OI to06 are operated according to the called line digits registered in theconnected finder-register circuits. At this time the PR. relays of thepermutation control link 01.2 are locked operated in the samecombination as that existing in the one or the other of permutationlinks PLI and PL2; and the translating circuit proceeds to operate thatcombination of the PR relays of control link CLI which representsboththe existing connections and the new desired connections between theincoming trunk circuits and the outgoing trunk circuits which aremultipled to the incoming and outgoing conductors respectively of thepermutation links PLI and PL2. When the control link CLI has been setunder the control of the translating circuit, the PR relays of thecontrol link GL2 and the PR relays of the idle one of the permutationlinks are operated in the same combination. When the new combination isset up by one of the permutation links, the other permutation link isreleased and the gate circuit operates to return the finder-registers inquestion to normal. The outgoing trunk relays OI to 06 which wereoperated are then released, and the translating circuit is again readyfor operative-association with one or more of the finder-registercircuits. The R00 and PRB relays of the translating circuit and the PR.relays of control link CLI remain operated in the existing combinationuntil the gate circuit operates responsive to the'initiation of newcalls through one or more of the incoming trunk circuits.

Detailed description Assume that a call is initiated at station W, thatthe line LI is connected to incoming trunk circuit TI, that there are noother calls then existing through the group of incoming trunk circuitswhich are common to permutation links PLI and PL2, and that thepermutation link PL2 is set to the switching combination existing whenthe last preceding call through one of these incoming trunks wasterminated and that this combination is the one in which none of theswitching relays I to II are operated. In such a case, relay TF isnormal; relays I 91 and I98 of permutation link PL2 are operated; noneof the relays of permutation link PL2 are op erated; relay ULI isoperated and relay U112 is not operated; none of the outgoing trunkrelays O1 to 06 are operated; none of the relays of the permutationcontrol links CLI and CL2 are operated; and only relays PRR and R of thepermutation translating circuit are operated, these relays having beenlocked at the end of the next preceding call.

When a call is initiated at station W and line LI is connected toincoming trunk circuit TI, relay A of the trunk circuit is operated bythe energization of its windings in series with the line loop. Theoperation of relay A closes a circuit for operating relay B, wherebyrelay B connects ground to conductor I4 to hold any intermediateswitches or circuits included in the connection between line LI and thetrunk circuit T I. The operation of relay B also connects ground throughits lower contact, lower back contact of relay D and inner lower backcontact of relay BB, thence through conductor IT to mark the terminalset of this trunk in the bank of wiper 8 of the finder switch of each offinderregister circuits FRI and FRZ. The ground potential thus connectedto conductor I! is further connected through resistor RI of trunk TIthrough start conductor I0 and lowermost back contact of relay CT I offinder-register FRI, and through the interrupter contact of steppingmagnet FMI of the finder switch Fl to operate this stepping magnet andthereby advance the finder step by step until wiper 8 encounters theterminal to which conductor I1 is connected; whereupon relay CTI isoperated by the energization of its upper winding to prevent the furtheroperation of the stepping magnet. With relay CTI operated, a circuit isclosed for operating relay CT of trunk circuit TI, this circuit beingtraced from the winding of relay CT, through conductor I0, terminal andwiper 5 of finder switch Fl, a front contact of relay CTI, to ground ata back contact of relay BBI. With relay CT of the trunk and relay CTI ofthe finder-register circuit FRI operated, the line loop is transferredfrom the windings of the A relay of the trunk circuit, throughconductors II and I2, wipers 6 and I of switch FI and front contacts ofrelay CTI to the windings of relay AI of the finder-register circuit.Relays A and B of trunk circuit TI are thereby released so as todisconnect ground from conductor I0 and from start conductor I0. Withrelay CT of the trunk circuit operated, holding ground continues to beconnected to conductor I l. The operation of relay AI closes a circuitfor operating relay Bl. With relay BI operated, the start conductor isis extended through the lowermost front contacts of relays OTI and BI tothe next finderregister circuit.

When the subscriber at station W dials the number of the called line,relay AI alternately releases and reoperates as many times as there areunits in the digit dialed. The first release of relay Al closes acircuit for operating relay CI and the stepping magnet RMI of registerswitch RI, in parallel. This circuit is traced from ground through theback contact of relay AI, a front contact of relay BI and the upper backcontact of relay Cla. Relay CI locks operated independent of relay Claand closes circuits for operating relays Cla. and DI. Relays Cla locksindependent of relay CI and opens the operating circuit of relay CI.When relay AI reoperates, at the end of the first impulse, the steppingmagnet RMI releases, thereby stepping the wipers of switch RI to thefirst offnormal set of terminals. The next and each succeeding releaseand reoperation of relay AI causes a like operation and release ofstepping magnet RMI so as to advance the wipers of switch Rl to aposition corresponding to the digit dialed. Being slow to release,relays BI and CI remain operated during the receipt of dial impulses.Relay CI releases a predetermined interval of time after relay AIreoperates at the end of the last dial impulse. If the called linehappens to be busy, the test conductor connected to the terminal engagedby wiper 4 of switch RI is grounded; and, when relay CI releases, thebusy test relay BBI is operated. Assuming the register switch RI to beset in position 1, the circuit for operating relay BBI is traced fromthe winding of this relay, through the front contact of relay DI, middlelower front contact of relay C'la, back contact of relay CI, wiper l ofswitch RI, over the sleeve conductor 2I3 of trunk circuit 2Ill toground.

If relay BBI operates, due to the called trunk line being busy, it looksunder the sole control of relay Cla before relay DI releases. Therelease of relay CI causes the release of relay DI, but relay DI is slowin releasing to allow the test relay BBI to operate before theabovetraced operating circuit is opened. The release of relay DIconnects ground through the upper front contact of relay BI, inner backcontact of relay CI, lowermost front contact of relay Cla, lowermostback contact of relay DI, outer front contact of relay BBI, wiper I ofswitch FI and conductor I6, to operatively energize the winding of relayBB of trunk circuit TI. The operation of relay BBI disconnects groundfrom conductor I0, thereby to cause the release of relay CT of trunkcircuit TI, whereby relays AI and BI of the finder-register circuit FRIare released and relays A and B of trunk circuit Tl are reoperated. Therelease of relay Bl causes the release of relays CI'I, Old and BBI andcauses the operation of release magnet RLI, thereby restoring switch Rlto normal. When the switch RI reaches normal, the offnormal springs ON Iare restored to normal, causing the release of the release magnet RLI.The busy back relay BB in the trunk circuit TI locks under control ofrelays D and B and closes a path through condenser TC for transmittingbusy tone from the busy tone transformer BT to the calling station. Whenthe subscriber at the station W returns the telephone to normal, relaysA and B and BB release in succession.

If the called line is idle, the busy test relay BBI of finder-registercircuit FRI does not operate when its winding is connected, by therelease of relay CI, through wiper 4 of switch Rl to the sleeveconductor of the called trunk line. The release of relay CI causes therelease of relay DI thereby disconnecting the sleeve conductor of thecalled line from the winding of relay BBI and connecting this conductorthrough the inner lower back contact of relay DI and inner lower backcontact of relay BBI to ground at the upper front contact of relay Cla,thereby marking the called trunk line busy to prevent its selection byany other finder-registercircuit. The release of relay DI also closes aconnection from ground at the upper front contact of relay BI, throughthe inner back contact of relay CI, lowermost front contact of relayCla, outer lower back contact of relay DI, and outer lower back contactof relay BBI to conductor 88, thereby operating line relay ll of thegate circuitin. Fig. 4 providing gate relay lllli is at that time notoperated- Assuming that relay H30 isnormal and that relay ll operates,relay lfll locks to conductor 88 independent of relay I00 and connectsground to start conductor H8, thence through a back contact of relay ST2of the translating circuit and a front contact of relayPRR to operaterelay UL. Relays PRR and R00 and any of the relays of the controlpermutation link I which were operated and locked by the next precedingcall, are released when ground is disconnected from conductor M6 by theoperation of relay UL of the translating circuit. The release of relayPRR causes the release of relay UL, whereby the ground connected toconductor H8 is extended through back contacts of relays 8T2, PRR andUL, through another back contact of relay ST2, conductor H4, and backcontacts of relays m8 and I96 to the winding of gate relay 168, thuscausing the operation of gate relay I99. The release of relay UL alsocauses the operation of relay PTE, the operating circuit being tracedfrom the grounded start conductor l lll through a back contact of eachof relays T2, PRR, UL and PTC,

conductor 5?, a back contact of each of relays PT6, PT5, PT i, PT3, PT2and PTl, and conductor l5l to the winding of relay PTE. If there hadbeen no previous call or if the locking ground connected to conductor ishad been disconnected for instance, by a manual operation of relay UL,the connection of ground to conductor H8 when relay llil operates causesthe operation of relay IEO without first operating and then releasingrelay UL. The operation of relay lilll opens the operating circuit ofrelay Hi! and of all similar relays so as to prevent the operativeassociation of any other finder-register circuit with the permutationcontrol link and translating circuits while the finder-register circuitFRl is operatively associated therewith. Relay lill remains operatedsince it is locked to co; ductor 88 independent of relay I98. Theoperation of relay I88 causes the operation of relay I95; and, withrelay llll operated, ground is connected to conductor 81 to operaterelay SW l of the finderregister circuit FRI. Relay I86 locksindependent of relays ill and H2 and, then opens its operating circuit.Relay Hi8 does not operate at this time since its winding is shortcircuited by its own lower back contact. The ground connected toconductor 8'! is further extended through wiper 3 of register switch Rlin position I, and through conductor Oil to operate outgoing trunk relayOI of the translating circuit. The operation of relay SWI of thefinder-register circuit FRI closes a circuit through wiper 2 of switchFl and conductor 18 for operating relay RG of trunk circuit Tl; closes acircuit through wiper l of switch Fl and conductor it for operatingrelay BB of the trunk circuit Tl; opens the normally closed connectionbetween wipers l and 2 of switch Rl; opens the normally closedconnection between wipers 3 and 4 of switch Fl; closes a connectionbetween wiper 2 of switch. Rl and wiper l of switch Fl and closes aconnection between wiper l of switch RI and wiper 3 of switch Fl. Withrelays RG and BB of trunk circuit Tl operated, relay RG locks undercontrol of relays BB and B.

If while the foregoing operations are taking place, a call is originatedat station X and line L8 is connected to incoming trunk circuit T6, thistrunk circuit operates to start the finder switch offin'der-registercircuit FR2. When the wipers of finder switchFZ makecontact with theterminals connected to trunk circuit T6, relay CT of the trunk circuitand relay GT2 of the finderregister circuit are operated; relays A and Bof the trunk circuit release; and relays A2 and B2 of finder-registercircuit PR2 are operated. When the subscriber at station X dials thenumber of the called line, the register switch R2 is advanced to acorresponding position. If the called line is idle, relay BB2 of theregister circuit does not operate and the called line is marked busythrough wiper 4 of switch R2. If relay lllil of the gate circuit hasbeen operated, the line relay )2 cannot operate to connect thefinder-register circuit PR2 to the permutation control link andtranslating circuits and the switching. relay SW2 cannot beimmediatelyoperated; in which case, the call from station X must now wait forrelease of the permutation control link and translating circuits.However, if both of relays lfil and I62 in the gate circuit should beoperated before gate relay Hi8 operates, theoperation of relay I20effects both the operation of relay SWl of finderregister FRI and theoperation of relay SW2 in finder-register PR2; whereby relays RG and BBof trunk circuit T8 are operated and, assuming register switch R2 to beset in position 2, a circuit is closed through wiper 3 of switch R2 andconductor O2l for operating outgoing trunkrelay O2 in the translating.circuit.

With both of relays SW! and SW2 operated, the aforementioned operationof relay PTE of the translating circuit closes a connection from thegrounded start conductor H8 through a back contact of each of relaysST2, PRR, UL, PTC, and PTlEa, a front contact of relay PTE, conductorI86, back contact of relay O6, conductor l'lfi, a back contact of eachof relays PR3, PR2 and PRl of control link 0L2, conductor $3, Wiper 3 ofswitch F2 of finder-register FRl, front contact of relay SW2, wiper l ofswitch R2 in position 2, conductor 023, a front contact of outgoingtrunk relay O2, conductor llE, a back contact of each of relays PRl l,Pal-a, Pas, PR8, Pm, PR6, PR5,

PR4, PR3, PR2 and PRl of control link 0L2, conductor 23, a back contactof relay CT of incoming trunk circuit T2 (which is not shown), conductor29, a back contact of each of relays PRi, PR2, PR3, PR4, PR5, PR5, PR1,PR8, PR9, PRlll and PRll of control link CLl, conductor I62, 2. backcontact of relay ROC of the translating circuit to the lower winding ofrelay PT2.

The operation of relay PT2 closes a circuit for operating relay PRi ofcontrol link CLl this circuit being traced from the winding or relay PR!through conductor i725, a back contact of each of translating circuitrelays PTfi and PTB, a front contact of relay PT2, conductor 32, a frontcontact of relay PTE, a back contact of relay PTB, and a back contact ofeach of relays UL, PRR and ST'Z to the grounded start conductor llli.Relay PR4 looks through conductor Hill to ground at a back contact ofrelay UL in the translating circuit. With relay PRl of control link CLloperated, conductor 2% is transferred to open the operating circuit ofrelay PTZ and close an operating circuit for relay PTS, thereby causingthe release of relay PT2 and the operation of relay PIS. The operatingcircuit of relay PT3 is traced from conductor 29 through a front contactof relay PRA and a. back contact of each of relays PR2, PR3, PR3, PR5,PR6, PR7, PR3, PR9 and PRllLcondu-ct'or M3, aback contact ofrelay ROC.to the lower winding of relay PT3. The operae tion of relay PT3 closesa circuit for operating relay PR3 of control link CLI, which circuit istraced from the winding of relay PR3 through conductor I23, a backcontact of relay PTE and a front contact of relay PT3 to the groundedconductor I52. Relay PR3 locks to conductor I40; opens the operatingcircuit of relay PT3, whereby relay PT3 releases; and closes a circuitfor operating relay PT6. This circuit includes the aforementionedconductor 29, a front contact of relay PRI, a back contact of relay PR2,a front contact of relay PR3, conductor I46, a back contact of relay ROCand the lower winding of relay PT6. With relay PTG operated, a circuitis closed for operating relay PTO; this circuit is traced from thewinding of relay PTO through conductor I53, a back contact of each ofrelays PTI, PT2, PT3, PT4 and PT5, a front contact of relay PT6,conductor I61, a back contact of each of relays PTC, UL, PRR and ST2 andthe grounded start conductor IIB. With relay PT6 operated, the operatingcircuit of relay PTE is open and with relay PTQ operated, the lockingcircuit of relay PTE is opened, wherefore relay PTE releases. Theaforementioned operation of relay PTO also opens the connection betweenconductor I 52 and the grounded start conductor IIO. The release ofrelay PTE closes a locking circuit for relay PTO; closes a connectionfrom conductor I54 through a front contact of relay PTO and a backcontact of each of relays PTE, UL, PRR and ST2 to the grounded startingconductor I I8; and disconnects ground from conductor I86 by opening itsconnection with conductor I61, whereby the lower winding of relay PT6 isdeenergized. With ground connected to conductor I54 and with relay PTEoperated, a circuit is closed for operatively energizing the winding ofrelay PT6a in parallel with the upper winding of relay PTO. Theoperation of relay PTrSa connects these windings directly to conductorI61 whereby relays PTB and PTEa are looked under the control of relaysPTO, UL, PRR and ST2 to the grounded start conductor H8.

With relay PTBa operated, the grounded conductor I61 is connectedthrough a front contact of relay RIM and a back contact of relay PT5a toconductor I 85; and, with outgoing trunk relay 05 not operated, thisconnection is extended through a back contact of relay O5, conductorI15, a back contact of each of relays PR6, PR5, PR4, PR3, PR2 and PRI ofcontrol link GL2, conductor 53, a back contact of relay CT of trunkcircuit T5 (not shown), conductor 59, a front contact of relay PRI ofcontrol link CLI, a back contact of relay PR2, a front contact of relayPR3, a back contact of each of relays PR4, PR5, PR5, PR1, PR8, PR9 andPRI O, conductor I43, a back contact of relay R00, to the lower windingof relay PT3. Relay PT3 is thereby operated, and a connection is closedfrom grounded conductor I54, through a front contact of relay PT3, afront contact of relay PT6, a back contact of relay PT5, and conductorI25 for operating relay PR5 of control link CLI. Relay PR5 locks toconductor I40, opens the above-traced operating. circuit of relay PT3and closes a connection from grounded conductor 59 for operating relayPT5; this connection is traced from conductor 59 through a front contactof relay PRI a back contact of relay PR2, a front contact of relay PR3,a back contact of relay PR4, a front contact of relay PR5, a backcontact of relay PR6, conductor I45 and a back contact of relay R00 tothe lower winding of relay PT5; The operation of relay PT5 closes acircuit for operating relay PTE, this circuit being traced throughconductor I5I, a back contact of each of relays PTI, PT2, PT3 and PT4, afront contact of each of relays PT5 and PTO and grounded conductor I61.The operation of relay PTE dis-connects ground from conductor I54 andopens. the locking circuit of relay PTO. Since the operating circuit ofrelay PTO is opened by the operation of relay PT5, relay PTO releases;whereby the grounded conductor I I8 is again connected to conductor I52,and this connection is extended through a front. contact of relay PT6a,a front contact of relay PT5, and a back contact of relay PT5a tooperatively energize the winding of relay PT5a and the upper winding orrelay PT5 in parallel. Relay PT5a closes a locking circuit to conductorI61 for holding relays PT5a and PT5 operated under the control of relaysPTC, UL, PRR and ST2 to the grounded start .conductor II8. The operationof relay PT5a transfers the connection of grounded conductor I61 fromconductor I to conductor I84, thereby causing the deenergization of thelower winding of relay PT5.

With outgoing trunk relay 04 not operated, the ground connection toconductor I84 is ex.- tended through a back contact of relay 04, conductor I14, a back contact of each of relays PR8, PR1, PR6, PR5, PR4,PR3, PR2, and PRI of control link GL2, conductor 43, a back contact ofrelay CT of incoming trunk circuit. T4 (not shown),conductor 49, a frontcontact of relay PRI of control link CLI, a back contact of relay PR2, afront contact of relay PR3, a back contact of relay PR4, a front contactof relay PR5, a back contact of each of relays PR6, PR1 and PR8,conductor I44, a back contact of relay R00 to the lower winding of relayPT4. Relay PT4 operates, closing a circuit for again operating relayPTO, this circuit being traced through conluctor I53, a back contact ofeach of relays PTI, 2T2 and PT3 and a front contact of each of relaysPT4, PT5 and PT6, to grounded conductor I 61. The operation of relay PTOdisconnects ground from conductor I52 and opens the lockin circuit ofrelay PTE; and relay PTE releases since its operating circuit was openedby the operation of relay PT4. With relay PTE released and relay PTOoperated, the grounded conductor H8 is again connected to conductor I54;and this ground connection is extended through a front contact of eachof relays PT4, PT6, PT5 and PT5a and a back contact of relay PT la tothe winding of relay PT4a and the upper winding of relay PT4 inparallel. Relay PT4a operates, closing a locking circuit to conductor I61 for holding relays PT4 and PT4a operated under the control of relaysPTC, UL, PRR and ST2 to the grounded start conductor H8. The operationof relay PT4a transfers the connection of grounded conductor I61 fromconductor I84 to conductor I83, thereby causing the deenergization ofthe lower winding of relay PT4.

With outgoing trunk relay 03 not operated, the ground connection toconductor I83 is extended through a back contact of relay O3, conductorI13, a back contact of each of relays PRIO to PRI of control link GL2,conductor 33, a back contact of relay CT in trunk circuit T3 (notshown), conductor 39, a front contact of relay PRI of control link CLI,a back contact of relay PR2, a front contact of relay PR3, a backcontact of relay PR4, a front contact of relay PR5, a back contact ofeach of relays PR6 to PRIO,

11 conductor I43, a back contact of relay R to the lowerwinding of relayP'13. Relay PT3 operates. closing a circuit for a ain operating relayPTE,-this circuit being traced through conductor H, a back contact ofeach of relays PTI and PT2, a front contact of each of relays PT3, PT4,PT5 and PTG to grounded conductor I 61. The operation of relay PTEdisconnects ground from conductor I54 and opens the locking circuit ofPTI]; and relay PTI releases since its operating was opened by theoperation of relay PT3. With relay PTO released and relav PTE operated,the grounded start conductor H8 is again connected to conductor I52; andthis ground connection is extended through a front contact of each ofre- Plays PTGa, PT5, PTEa, PT4a and PT3, and a back con -act of relayPT3a to the winding of relay RIM and the upper winding of relay 'PTS inparallel. Relay PTSa operates, closing a looking circuit to conductor I51 for holding relays PI'3 and PISa o erated under the control of relaysPTC, UL, PRR and ST?! to the grounded start conductor H8. The operationof relay PT3u. transfers the connection of grounded conductor I61 fromconductor I 83 to conductor I82. thereby causing the deenergization ofthe lower winding of relay PT3.

With outgoing trunk relav O2 operated, the ground conne tion toconductor I82 is "extended throu h the front contact o'frel'av O2,conductor O22, wiper 2 of re ister R2'o'f finder-register PR2, afrontcontactof relay SW2. Winter 4 of finder switch F2,c' nductor 65. afront contact of each nfrela s BB andCT of incoming trunk c r uit T6,conduct r 69, a front contact of relay PRI of con rol link CLI, a backcontact of relay PR2, a front c ntact of rela PR3, a back contact ofrelay PR4. a front contact of relay PR5, aback contact of ea h of relaysPR9. PR1, PR8, PR9, PRIIl and PRII, conductor I4I. a black contact ofrelay ROCto the lower winding of relay PTI. Relay PTI operates,'closlng'a circuit for operating relay PR! I of control link CLI, whichcircuit is tra ed through conductor I31, a back contact of relay PTZ,and a front contact "of each of relays PT3, PM and PTI to groundedconductor I52. Relay PRI'I locks to conductor I 49 and transfers "theabove traced ground connection which includes conductors I82 and 69 fromconductor I4I to conductor I42, thereby releasing relay PTI and'op'eratively energizing the lower winding 'of relay PTZ. The operationof relay PTZ closes a circuit'for operating relay -PTI), this circuitbeing traced through conductor I53, "aback contact of relay PTI, a frontcontact of each of relays'PT2, P'I3, PT4, PIE "and PTB to -groundedconductor I51. This operation of relay PTfl disconnects ground fromconductor I52 and opens the locking circuit of relay PTE'; and relay PTEreleases since its operating circuit was opened by the operation ofrelay PT2. With relay PTE released and relay PTI! operated, the groundedstart conductor I I8 is again connected to conductor I54, and thisground connection is extended through a front contact of each of relaysPT4, PTB, -PT5, P'IEa, PT Ia, PT3a. and PT2, conductor I58, 'a backcontact of relay PIZa to the winding of relay PI2a and the upper windingof relay PM in parallel. Relay PTZa operates, closing a locking circuit'to conductor I61 for holding relays PT2 and PT2a operated under thecon- -tro1 of relays PTC, UL, PRR and em to the grounded start conductorI I8. The operation of relay P'I'Za transfers the connection of grounded12 conductor I61 from conductor I82 to conductor IBI, thereby causingthe deenergization of the lower winding of relay PTZ.

With outgoing trunk relay OI operated, the ground connection toconductor I8! is extended through a front contact 'of relay OI,conductor OIZ, wiper 2 of register RI of finder-register FRI, a frontcontact of relay SW1, wiper 4 of finder switch FI, conductor I5, a frontcontact of each of relays BB and CT of trunk circuit Ti, conductor I9, afront contact of relay PRI of control link CLI, a back contact of relayPR2, a front contact of relay PR3, a back contact of relay PR4, a frontcontact of relay PR5, a back contact of each of relays PR6, PR1, PR8,PR9 and PRIO, a front contact of relay PRI I, conductor I 4|, a backcontact of relay R00, to the lower winding of relay PTI. Relay PTIoperates and is looked through a front contact of each of relays PT2,PT3, PT4, PT5 and P'Ifi to grounded conductor I61. The operation ofrelay PTI closes a circuit for operating relay ROC, which circuit istraced through conductor I59, a front contact of relay PTZa, conductor Iand a front contact of relay PTI. Relay ROC locks to conductor I40,opens the connections between the lower windings of relays PTI to PT6and conductors I4! to I49, connects ground to conductors I39 and I48 andcloses a circuit for operating relay PTC; which circuit is tracedthrough conductor I41 and a front contact of relay ROC, thence inparallel with the upper winding of relay PTI, through the locking frontcontact of relay PTI, a front contact of each of relays PT2 to PTG,conductor I61, inner upper back contact of relay PTC and a back contactof each of relays UL, PRR and ST2 to the grounded start conductor II9.Relay PTC closes its uppermost front contact so as to lock to the startconductor independent of the relays ROC and PTI to PT6, inclusive,before its operating circuit is opened at the upper back contacts ofthis relay. With relay PTC operated, conductor I91 is disconnected fromthe grounded start conductor H8 thereby causing the release of relaysPTI to PTG, PT2a to P'IBa and PTO. Relay PRR does not operate at thistime since its operating circuit is opened by the operation of relayPTC. ,Since it has been assumed that none of the PR relays of link 'CL2were operated, relay I18 is not operated and it is not necessary tooperate relay I19 to unlock and release the PR relays of this link.However, if any of the PR relays and relay I18 of link GL2 are operatedat the time relay PTC of the translating circuit operates, an operatingcircuit is closed for relay I19; and the operation of relay I19 effectsthe release of the PR relays of link GL2 followed by the successiverelease of relays I18 and I19. The circuit for operating relay I19includes the inner front contact of relay I18, conductor I88, a backcontact of relay STZ of the translating circuit, the lower front contactof relay PTC, conductor I48, and a front contact of relay ROC. With bothof relays I18 and I19 released and with relay ULI operated ashereinbefore stated, a circuit is closed for operatively energizing thelower winding of relay ST2 0f the translator circuit. This circuit istraced through conductor I81, a back contact of each of relays I18 andI19, conductor I89, a front contact of relay ULI, a back contact ofrelay UL2, conductor I99, a continuity back contact of relay S'I'Z, thelower front contact of relay PTC, conductor I48 and a front contact ofrelay ROC.

1-3 Relay ST2 operates and closes a locking circuit through its upperwinding and inner upper front contact to grounded start conductor II8.Relay 8T2 first connects ground directly to conductor II4 so as tocontinue to hold the gate relay I00, and then opens the connectionbetween conductor H4 and the grounded start conductor I I8. Theoperation of relay STZ also connects ground directly to conductor I90 tomaintain the energization of its lower winding until the condition ofone of the ULI and UL2 relays changes. The operation of relay ST2 alsoopens the connection between start conductor H8 and the upper transfercontact spring of relay PRR and closes circuits for operating the PRrelays of permutation link PLI in accordance with the setting of the PRrelays of control link CLI. These circuits are traced from ground at theback contact of relay II2 of the gate circuit, through conductor II'I,lowermost front contact of relay STZ, conductor II 9, thence through a.front contact of each of the operated PR relays of control link CLI,through the corresponding conductors in the group CWI to CWI I,inclusive, back contacts of relay TF, corresponding conductors in thegroup AWI to AWI I, inclusive, to the windings of the corresponding PRrelays of link PLI. Since in the case assumed, relays PRI, PR3, PR andPRII of control link CLI have been operated, switching relays PRI, PR9,PR5, and PRI I of link PLI operate. At the same time, the correspondingones of relays PRI to PRII of control link GL2 are operated since thewindings of these relays are also connected to conductors CWI to CWI Irespectively; that is, relays PRI, PR3, PR5 and PRII of link GL2 operateand lock through conductor I80 to ground at a back contact of relay I19.The operation of these relays of control link CLZ closes a circuit foroperating relay I18; and relay I79 closes a circuit for operating gaterelease relay III, this circuit being traced through conductor I I0,outer front contact of relay IIB, back contact of relay I79, conductorI89, front contact of relay ULI, back contact of UL2, conductor I99 toground at a front contact of relay STZ. The operation of relay I IIcloses a circuit for operating relay IIZ. Relay I I2 locks under controlof relay I99, disconnects ground from conductor II'l, thereby preventingthe further operation of PR relays of control link (IL-2 and permutationlink PLI The aforementioned operation of relay III opened the shortcircuit around the winding of relay 108 so that relay I08 operates.Relay I00 is held operated until relays IN and H2 release. The operationof relay I00 connects ground to conductor H5 operating transfer relayTF. Relay TF disconnects ground from conductor I92 and connects groundto conductor I9I, operating relays I95 and I95; whereby connections areestablished between incoming trunk circuit TI and outgoing trunk circuit2I0 and between incoming trunk circuit T6 and outgoing trunk cir-.

,With relays I06, I08 and H2 operated, the release of relay III causesthe operation of relay H3; relay 3 looks through conductor! to ground ata front contact of relay STZ. When all of the relays of link PL2 havereleased, relay ULI releases thereby connecting ground to conductor I93to lock relays I95 and I99 and the operated PR relays of link PLI. Therelease of relay ULI causes the reoperation of release relay HI, therebyconnecting ground through a front contact of relay H3 and front contactsof relays IOI and I02, to conductors 89 and 99 to operate the BBI andBB2 relays of finder-register circuits FRI and FR2. Each of the BBI andBB2 relays locks under control of the associated one of relays Chi and02a; disconnects ground from wiper 5 of the associated finder FI or F2,thereby causing the release of relays CT of the associated incomingtrunk circuits TI and T6; and disconnects ground from conductorsv 89 and99, respectively, thereby causingthe release of. relays NH and I02 ofthe gate circuit. The release of relays MI and I02 disconnects groundfrom conductor H8 thereby causing the release of relay ST2 of thetranslating circuit. The release of relay IOI disconnects ground fromconductor 8! and the release of relay I02 disconnects ground fromconductor 91, whereby relays SWI and SW2 of the finder-register circuitsFRI and PR2 and outgoing trunk relays OI and 0-2 of the translatingcircuit are released. The release of relay STZ disconnects ground fromconductors I I4 and I90. When ground is disconnected from conductor II4,relays I09 and H3 of the gate circuit release; and,'when ground isdisconnected from conductor I90, relay III releases. The release ofrelay I00 causes the release of relay H2. Relays I06 and I08 remainoperated to connect the winding of gate relay I90 to conductor H0 foroperation on the next call, during which relays I09 and I08 arereleasedin turn instead of being operated in turn as above described. Relay TFalso remains operated until the next call or calls have been receivedand extended.-

The aforementioned release of relay CT in each of trunk circuits TI andT6 disconnects the lines LI and L9 from the windings of the AI and A2relays respectively in the finder-register circu ts, and reconnectsthese lines to the windings of the A relays of the trunk circuits,thereby reoperating the A and B relays of each of trunk circuits TI andT9. The release of the AI relay of finder-register FRI causes therelease of relay BI; and the release of relay BI causes the release ofrelays CTI and Cla. The release of relay CTI disconnects the windings ofrelay AI- from con- .ductors I I and I2 and reconnects start conductorI9 to the stepping magnet FMI of finder FI. The aforementioned releaseof relay BI also causes the operation of release magnet RLI of registerswitch RI, whereby this switch is restored to normal. The circuit foroperating release magnet RLI is opened at contacts ONI .when the wipersreach normal position. The

finder-register FRZ is restored to normal in like manner.

The aforementioned release of relay CT of trunk circuit TI closes acircuit from ringing generator 9, through the middle winding of relay D,middle lower front contact of relay RG, conductor 8! through a frontcontact of relay I and contacts of the PR relays and a front contact ofrelay I96 of link PLI, conductor 2I2 of the selected outgoing trunk orline, through the ringer (not shown) at the called station Y, backthrough conductor 2| I, through a front contact of relay I96 andcontacts of the PR relays anda front contact of relay I95 or link'PLi,conductor TI, and a front contact of relay RG, to ground. Audibleringing tone is transmitted from conductor 8| through condenser TC tothe calling station. When the call is answered at station Y, relay Doperates, releasing relays BB and RG and reversing the current over theconductors of line Ll. With relays BB and RG released, the ringingcircuit is opened and relay D is held operated by the energization ofits upper and lower windings in series with conductors H and 8!, theconnection through link PLI, conductors 2H and H2 and the calledstation. Talking battery is fed to the calling line through the windingsof relay A and to the called line through the windings of relay D; andtalking current is transmitted through talking condensers TCi and TC2.When the called station is restored to normal, relay D releases; and,when the calling station is restored to normal, relay A releases. Therelease of relay A causes the release of relay B. The release of eitherof relays D or B disconnects the busy marking ground from conductor 9|.

The release of relay CT of trunk circuit T2 closes a similar circuitfrom generator 9 through link PL! for ringing the called station Z.Relay D operates when the call is answered and relays BB and RG release.Relays A and D remain operated until the calling and called stationsrestore their telephones to normal. When relays A and D release, relay Bis released. The release of either of relays D or B disconnects busymarking ground from conductor 96.

A soon as another call is initiated, the calling line is extended to afinder-register, the called line digit is registered, the gate circuitoperates to associate the finder-register with the translating circuit,and the foregoing cycle of operations is repeated to establish the newdesired connection and maintain the previous connections which have notbeen terminated. The relays of the translating circuit and permutationcontrol links which are operated depend upon what connections arerequired. The following table indicates the control link PR relays whichare controlled when ground is successively connected to each ofconductors I85, 185, I64, 423 and I82 and indicates which of the PTE andPT!) relays is operated.

Ground C nnected to PTO PR Relays Gon- Ccnduct-or Operated trolled PR1,PR2, PR3.

PR4, PR5, PR6.

. PR7. PR8.

PR9, PRlO.

PR ll.

Upon connection of ground to any one of condustors 135 to Isl, thisground is extended under the control of outgoing trunk relays andcontrol links CL! and GL2 to the required one or more of conductors it!to I48 depending upon which of the outgoing trunk relays OI to OS areoperated and what PR relays of control link GL2 are operated at thattime. The PR relays of control link cm which are operated when ground isconnected from each of conductors I86- to I81 to each one of conductorsMl to M6 is indicated by the following table:

Control link Translating Ground connected To con- PR relays relay oper-[rom conductor ductor operated ated PR2, PR3..

Intermediate ones of the translating relays PT! to PT? may be operatedand released to finally effect the operation of the PR and PT relaysaccording to the above table.

The intermediate trunk circuit shown in Fig. 11 is similar to theincoming trunk circuits TI and T6 except that it lacks means forcontrolling ringing and is not arranged to supply talking battery tocalling and called lines. Intermediate trunks may be connected betweentwo sets of permutation links each of which is similar to links PLI andPLZ; and each set of permutation links will have associated therewithcontrol links and a translating circuit similar to those hereinbeforedescribed.

What is claimed is:

l. A switching device comprising a plurality of incoming conductors, aplurality of outgoing conductors, electromagnetically actuated contactmeans for simultaneously establishing individual direct metallicconnections between said incoming and outgoing conductors in any desiredpermutation, a plurality of electromagnets controlling said contactmeans, and control means for selectively energizing any one or anycombination of two or more of said electromagnets.

2. In a switching device, a plurality of incoming conductors and a likeplurality of outgoing conductors, contact means for simultaneouslyconnecting said incoming conductors to said outgoing conductors in anydesired permutation, said contact means divided into a plurality ofswitching stages, each stage comprising one or more relays, each relayhaving sets or transfer and output contacts, each relay of a stagecontrolling a plurality of sets of switching contacts, the number ofsets of contacts controlled by each relay in a first stage being equalin number to said plurality of incoming conductors and the number ofsets of contacts controlled by each relay in each succeeding stage beingone less than the number of sets of contacts controlled by each relay ofthe preceding stage, conductors individually connecting the transfercontacts of each relay except the first relay of the first stage tooutput contacts of the next preceding relay, said incoming conductorsbeing individually connected to transfer contacts of the first relay ofthe first stage, said outgoing conductors being individually connectedto output contacts of the last relays of said stages, and means forselectively operating said relays to establish individual connections inany desired permutation between said incoming and outgoing conductors.

3. In a switching device, a plurality of incoming conductors and a likeplurality of outgoing conductors, contact means for simultaneouslyconnecting said incoming conductors to said outgoing conductors in anydesired permutation, said contact means divided into five stages, thelast stage comprising one relay having two sets of transfer and outputcontacts, the fourth stage comprising two relays each having three setsof transfer and output contacts, the third stage comprising two relayseach having four sets of transfer and output contacts, the second stagecomprising two relays each having five sets of transfer and outputcontacts and the first stage comprising two relays each having six setsof transfer and output contacts, conductors individually connecting thetransfer contacts of each relay except the last to output contacts ofthe next preceding relay, said incoming conductors being individuallyconnected to transfer contacts of the first relay of the first stage,said outgoing conductors being individually connected to output contactsof the last relays of said stages, and means for selectively operatingsaid relays to establish individual connections in any desiredpermutation between said incoming and outgoing conductors.

4. A switching device comprising a plurality of first conductors, aplurality of second conductors, a plurality of switching stages eachcomprising one or more relays having contacts establishing individualdirect metallic connections between conductors incoming to the stage andconductors outgoing from the stage, the last stage having two incomingand two outgoing conductors and each stage other than said last stagehaving one more incoming and one more outgoing conductor than thesucceeding stage, said first conductors constituting the incomingconductors of the first stage, the outgoing conductors of each stageother than the last con-' stituting the incoming conductors of the nextsucceeding stage, one outgoing conductor of each stage other than thelast and both outgoing conductors of the last stage constituting saidsecond conductors, and means for selectively changing the operativecondition of said relays to individually connect said first conductorsto said second conductors in any desired permutation.

5. In a switching system, a plurality of incoming lines and a likeplurality of outgoing lines, first and second permutation switchinglinks common to said incoming and outgoing lines, each of said linkscomprising a series of relays having sets of transfer and outputcontacts and conductors individually connecting the transfer contacts ofeach relay except the first to output contacts of the next precedingrelay, said incoming lines connected to the transfer contacts of thefirst relay of both links, one of the output contacts of each relayexcept the first and the output contacts of the last relay of each linkbeing connected to said outgoing lines, said relays of each link beingselectively operable to connect said incoming lines to said outgoinglines in any desired permutation, control means comprising relays commonto said lines and said links for effecting the selective operation ofthe relays of one of said links to interconnect said incoming lines andoutgoing lines in a desired permutation and for thereafter effecting theselective operation of the relays of the other of said links tointerconnect said incoming and outgoing lines in a different desiredpermutation.

6. In a switching system, a plurality of incoming lines and a likeplurality of outgoing lines,

first and second permutation links common to said incoming and outgoinglines, each of said permutation links comprising electromagneticswitching means adapted to establish individual connections between saidincoming lines and said outgoing lines in any desired permutation, saidfirst link operated at one time to interconnect said incoming andoutgoing lines in a particular permutation and said second link beingreleased, control means common to said lines and links for operatingeither link to interconnect said incoming and outgoing lines in anydesired permutation, said control means comprising third and fourthpermutation links, each of said third and fourth links comprisingelectromagnetic switching means selectively operable to individuallyconnect a number of input control conductors to alike number of outgoingcontrol conductors in any desired permutation, the number of inputcontrol conductors of said third and fourth links being equal to saidplurality of incoming lines, control relay means for operating saidthird link in the same permutation as that in which said first link isoperated, register means registering one or more desired connectionsbetween incoming and outgoing lines, control relay means for operatingsaid fourth link in the permutation in which said second link is to beoperated to include said registered desired connections between incomingand outgoing lines and maintain all other connections existing throughsaid first link, and control relay means for operating said second linkin the same permutation as is said fourth link and for thereuponreleasing said first link.

7. In a switching system, a switching device comprising a plurality ofincoming conductors, a plurality of outgoing conductors, electromagneticmeans having contacts simultaneously establishing individual metallicconnections between said incoming and outgoing conductors, saidelectromagnetic means being variably operable to establish theinterconnection of said incoming and outgoing conductors in any desiredpermutation, means for registering desired connections between one ormore of said incoming conductors and the desired one or more of saidoutgoing conductors, and control means including translating relayscontrolled by said register means for selectively operating theelectromagnetic means of said switching device to establish saidregistered desired connections and continue the previously existingconnections between all other incoming and outgoing conductors.

8. In a switching system, a, plurality of incoming lines, a likeplurality of outgoing lines, a switching device comprising two likeseries of relays each series selectively operable to interconnect saidincoming and outgoing lines in any desired permutation, the relays ofeither series operated at one time to interconnect said lines in aparticular one of said permutations while the other set is released andwaiting operation, a first register means comprising a number of relaysselectively operable to interconnect a number of incoming control and alike number of outgoing control conductors in any desired permutation,said number of incoming conductors being equal to said plurality ofincoming lines and the number of register relays being equal to thenumber of relays in each of said series, means for connecting the relaysof said first register means in parallel with the relays of the oneseries Which is then operated thereby to operate the relays of saidfirst register means corresponding

